I have a '86 mustang lx and i recently put a new heater core in,and after i reconnected my head light switch someting sparked on or near my fuse box now my dash board lights and my temp.and gas gauge doesn't work. all my fuses are good but i have no clue on what to do.

 

try posting this in the 6 cyl/ 4 cyl. section...maybe jugador will see it

 

you probably crossed a (or a few) wires, which is shorting out the circuit. common mistake for rookie electronic dudes. just double check your wiring, and if you did any soldering, use heat shrink to cover up your solder joints. you can get heat shrink at radioshack for like 2 bucks.